In completing production or injection wells in the oil and gas industry, it is common practice to run various downhole tools into the wellbore in a retracted or “run-in” position and then set or actuate the downhole tool once reaching a target destination. Such downhole tools are normally run into the wellbore on some type of running tool, which, in turn, is releasably connected, to the lower end of a tubing string conveyance extended from a surface location. After the downhole tool is set within the wellbore, the running tool is then released from the downhole tool and withdrawn from the wellbore along with the tubing string.
Some running tools incorporate the use of shearable elements (e.g., shear pins, shear rings, etc.) to protect against premature disconnection of the running tool from the downhole tool when the running tool is rotated in a direction that would normally disconnect the running tool from the well tool. Unfortunately, such shearable elements frequently undergo substantial wear before the downhole tool assembly reaches its target destination, which can result in premature shearing and, therefore, premature setting of the downhole tool or disconnection of the running tool. This possibility is especially present in the modern, long and heavy downhole tool assemblies required for completing long production intervals and in those downhole tool assemblies required to complete production intervals in horizontal or inclined wellbores where the forces exerted on any shearable elements during installation can be substantial.
One proposed solution for preventing the premature shearing of the shearable elements is to include additional or stronger shearable elements. However, as may be expected, for a shearable element to be strong enough to prevent premature shearing, the force required to deliberately shear the shearable element be more than can be developed through the tubing string on which the downhole tool assembly is carried. Further, there may be instances where the downhole tool assembly becomes stuck in the wellbore before it reaches its target destination. When this occurs, it is highly desirable to be able to release the running tool and recover it along with the tubing string from the wellbore without the need for first setting the downhole tool.